MSH1: A NOVEL INTERORGANELLAR ENVIRONMENTAL RESPONSE IN HIGHER PLANTS

Plant organelles play essential and multifaceted parts in the environmental sensing and response

process. We know this not only because they serve as cellular sites for phytohormone

biosynthesis, but because they comprise the light and energy processing centers of the cell. Our

aim in this research is to enhance our understanding of photosynthetic components in environmental

sensing and response in plants. We will focus on the specialized plastids found in epidermal

and vascular cells that appear to condition environmental responses. In this project, we

seek to investigate the timing and nature of the plastid signal that produces stress response,

and to identify other possible components of the MSH1 system. MSH1 disruption results in particular

redox changes within the plant that appear to be conditioned in the plastoglobule, an unusual

subcompartment within the plastid. We aim to test whether these plastoglobular changes

participate in plastid-nuclear signaling that triggers altered growth responses in the plant that

affect vernalization, growth rate, clock gene response, flower time, transition to maturity, and

abiotic stress response. We speculate that MSH1 functions within specialized sensory plastids,

and we will analyze the transcriptome of cells in which MSH1 resides to better understand the

spatial and temporal context of its function. We pose the central hypothesis that a plastid-derived

signal gives rise to specific cellular changes associated with altered growth performance.

If correct, we expect to identify key components of this signaling process and to find

them conserved as the MSH1 process is played out across multiple plant species. The importance

of this work, and relevance to the DOE Energy Biosciences mission, lies in discovery

of novel components of the photosynthetic apparatus that influence growth behavior of the

plant.